// Copyright (c) 2010 Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
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// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef CLIENT_LINUX_HANDLER_EXCEPTION_HANDLER_H_
#define CLIENT_LINUX_HANDLER_EXCEPTION_HANDLER_H_

#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <sys/ucontext.h>

#include <string>

#include "client/linux/crash_generation/crash_generation_client.h"
#include "client/linux/handler/minidump_descriptor.h"
#include "client/linux/minidump_writer/minidump_writer.h"
#include "common/scoped_ptr.h"
#include "common/using_std_string.h"
#include "google_breakpad/common/minidump_format.h"

namespace google_breakpad {

// ExceptionHandler
//
// ExceptionHandler can write a minidump file when an exception occurs,
// or when WriteMinidump() is called explicitly by your program.
//
// To have the exception handler write minidumps when an uncaught exception
// (crash) occurs, you should create an instance early in the execution
// of your program, and keep it around for the entire time you want to
// have crash handling active (typically, until shutdown).
// (NOTE): There should be only be one this kind of exception handler
// object per process.
//
// If you want to write minidumps without installing the exception handler,
// you can create an ExceptionHandler with install_handler set to false,
// then call WriteMinidump.  You can also use this technique if you want to
// use different minidump callbacks for different call sites.
//
// In either case, a callback function is called when a minidump is written,
// which receives the full path or file descriptor of the minidump.  The
// caller can collect and write additional application state to that minidump,
// and launch an external crash-reporting application.
//
// Caller should try to make the callbacks as crash-friendly as possible,
// it should avoid use heap memory allocation as much as possible.

    class ExceptionHandler {
    public:
        // A callback function to run before Breakpad performs any substantial
        // processing of an exception.  A FilterCallback is called before writing
        // a minidump.  |context| is the parameter supplied by the user as
        // callback_context when the handler was created.
        //
        // If a FilterCallback returns true, Breakpad will continue processing,
        // attempting to write a minidump.  If a FilterCallback returns false,
        // Breakpad  will immediately report the exception as unhandled without
        // writing a minidump, allowing another handler the opportunity to handle it.
        typedef bool (*FilterCallback)(void *context);

        // A callback function to run after the minidump has been written.
        // |descriptor| contains the file descriptor or file path containing the
        // minidump. |context| is the parameter supplied by the user as
        // callback_context when the handler was created.  |succeeded| indicates
        // whether a minidump file was successfully written.
        //
        // If an exception occurred and the callback returns true, Breakpad will
        // treat the exception as fully-handled, suppressing any other handlers from
        // being notified of the exception.  If the callback returns false, Breakpad
        // will treat the exception as unhandled, and allow another handler to handle
        // it. If there are no other handlers, Breakpad will report the exception to
        // the system as unhandled, allowing a debugger or native crash dialog the
        // opportunity to handle the exception.  Most callback implementations
        // should normally return the value of |succeeded|, or when they wish to
        // not report an exception of handled, false.  Callbacks will rarely want to
        // return true directly (unless |succeeded| is true).
        typedef bool (*MinidumpCallback)(const MinidumpDescriptor &descriptor,
                                         void *context,
                                         bool succeeded);

        typedef bool (*MinidumpWholeCallback)(const MinidumpDescriptor &descriptor,
                                              void *context,
                                              bool succeeded,
                                              char *crashReason,
                                              char *threadTrack);

        // In certain cases, a user may wish to handle the generation of the minidump
        // themselves. In this case, they can install a handler callback which is
        // called when a crash has occurred. If this function returns true, no other
        // processing of occurs and the process will shortly be crashed. If this
        // returns false, the normal processing continues.
        typedef bool (*HandlerCallback)(const void *crash_context,
                                        size_t crash_context_size,
                                        void *context);

        // Creates a new ExceptionHandler instance to handle writing minidumps.
        // Before writing a minidump, the optional |filter| callback will be called.
        // Its return value determines whether or not Breakpad should write a
        // minidump.  The minidump content will be written to the file path or file
        // descriptor from |descriptor|, and the optional |callback| is called after
        // writing the dump file, as described above.
        // If install_handler is true, then a minidump will be written whenever
        // an unhandled exception occurs.  If it is false, minidumps will only
        // be written when WriteMinidump is called.
        // If |server_fd| is valid, the minidump is generated out-of-process.  If it
        // is -1, in-process generation will always be used.
        ExceptionHandler(const MinidumpDescriptor &descriptor,
                         FilterCallback filter,
                         MinidumpCallback callback,
                         void *callback_context,
                         bool install_handler,
                         const int server_fd);

        ~ExceptionHandler();

        const MinidumpDescriptor &minidump_descriptor() const {
            return minidump_descriptor_;
        }

        void set_minidump_descriptor(const MinidumpDescriptor &descriptor) {
            minidump_descriptor_ = descriptor;
        }

        void set_crash_handler(HandlerCallback callback) {
            crash_handler_ = callback;
        }

        void set_whole_callback(MinidumpWholeCallback callback) {
            whole_callback_ = callback;
        }

        void set_crash_generation_client(CrashGenerationClient *client) {
            crash_generation_client_.reset(client);
        }

        // Writes a minidump immediately.  This can be used to capture the execution
        // state independently of a crash.
        // Returns true on success.
        // If the ExceptionHandler has been created with a path, a new file is
        // generated for each minidump.  The file path can be retrieved in the
        // MinidumpDescriptor passed to the MinidumpCallback or by accessing the
        // MinidumpDescriptor directly from the ExceptionHandler (with
        // minidump_descriptor()).
        // If the ExceptionHandler has been created with a file descriptor, the file
        // descriptor is repositioned to its beginning and the previous generated
        // minidump is overwritten.
        // Note that this method is not supposed to be called from a compromised
        // context as it uses the heap.
        bool WriteMinidump();

        // Convenience form of WriteMinidump which does not require an
        // ExceptionHandler instance.
        static bool WriteMinidump(const string &dump_path,
                                  MinidumpCallback callback,
                                  void *callback_context);

        // Write a minidump of |child| immediately.  This can be used to
        // capture the execution state of |child| independently of a crash.
        // Pass a meaningful |child_blamed_thread| to make that third_party.thread in
        // the child process the one from which a crash signature is
        // extracted.
        //
        // WARNING: the return of this function *must* happen before
        // the code that will eventually reap |child| executes.
        // Otherwise there's a pernicious race condition in which |child|
        // exits, is reaped, another process created with its pid, then that
        // new process dumped.
        static bool WriteMinidumpForChild(pid_t child,
                                          pid_t child_blamed_thread,
                                          const string &dump_path,
                                          MinidumpCallback callback,
                                          void *callback_context);

        // This structure is passed to minidump_writer.h:WriteMinidump via an opaque
        // blob. It shouldn't be needed in any user code.
        struct CrashContext {
            siginfo_t siginfo;
            pid_t tid;  // the crashing third_party.thread.
            ucontext_t context;
#if !defined(__ARM_EABI__) && !defined(__mips__)
            // #ifdef this out because FP state is not part of user ABI for Linux ARM.
            // In case of MIPS Linux FP state is already part of ucontext_t so
            // 'float_state' is not required.
            fpstate_t float_state;
#endif
        };

        // Returns whether out-of-process dump generation is used or not.
        bool IsOutOfProcess() const {
            return crash_generation_client_.get() != NULL;
        }

        // Add information about a memory mapping. This can be used if
        // a custom library loader is used that maps things in a way
        // that the linux dumper can't handle by reading the maps file.
        void AddMappingInfo(const string &name,
                            const uint8_t identifier[sizeof(MDGUID)],
                            uintptr_t start_address,
                            size_t mapping_size,
                            size_t file_offset);

        // Register a block of memory of length bytes starting at address ptr
        // to be copied to the minidump when a crash happens.
        void RegisterAppMemory(void *ptr, size_t length);

        // Unregister a block of memory that was registered with RegisterAppMemory.
        void UnregisterAppMemory(void *ptr);

        // Force signal handling for the specified signal.
        bool SimulateSignalDelivery(int sig);

        // Report a crash signal from an SA_SIGINFO signal handler.
        bool HandleSignal(int sig, siginfo_t *info, void *uc);

    private:
        // Save the old signal handlers and install new ones.
        static bool InstallHandlersLocked();

        // Restore the old signal handlers.
        static void RestoreHandlersLocked();

        void PreresolveSymbols();

        bool GenerateDump(CrashContext *context);

        void SendContinueSignalToChild();

        void WaitForContinueSignal();

        static void SignalHandler(int sig, siginfo_t *info, void *uc);

        static int ThreadEntry(void *arg);

        bool DoDump(pid_t crashing_process, const void *context,
                    size_t context_size);

        const FilterCallback filter_;
        const MinidumpCallback callback_;
        volatile MinidumpWholeCallback whole_callback_;
        void *const callback_context_;

        scoped_ptr<CrashGenerationClient> crash_generation_client_;

        MinidumpDescriptor minidump_descriptor_;

        // Must be volatile. The compiler is unaware of the code which runs in
        // the signal handler which reads this variable. Without volatile the
        // compiler is free to optimise away writes to this variable which it
        // believes are never read.
        volatile HandlerCallback crash_handler_;

        // We need to explicitly enable ptrace of parent processes on some
        // kernels, but we need to know the PID of the cloned process before we
        // can do this. We create a pipe which we can use to block the
        // cloned process after creating it, until we have explicitly enabled
        // ptrace. This is used to store the file descriptors for the pipe
        int fdes[2] = {-1, -1};

        // Callers can add extra info about mappings for cases where the
        // dumper code cannot extract enough information from /proc/<pid>/maps.
        MappingList mapping_list_;

        // Callers can request additional memory regions to be included in
        // the dump.
        AppMemoryList app_memory_list_;
    };

    typedef bool (*FirstChanceHandler)(int, siginfo_t *, void *);

    void SetFirstChanceExceptionHandler(FirstChanceHandler callback);

}  // namespace google_breakpad

#endif  // CLIENT_LINUX_HANDLER_EXCEPTION_HANDLER_H_
